| Alldoorsuk.Com Ltd | Slough | 2025 |
| Alldos (UK) Limited | Birmingham | 1996 |
| Alleben Ltd | London | 2026 |
| Allechi Limited | Mossley | 2024 |
| Allectra Limited | Lewes | 2003 |
| Allege Ltd | London | 2024 |
| Alleggra Foods Limited | East Molesey | 2004 |
| Allegiance Chemicals Ltd | Huddersfield | 2022 |
| Allegiance Services Limited | Gravesend | 2016 |
| Allegiant Stone Ltd | London | 2024 |
| Allegiant Systems Resource Ltd | Wimborne | 2024 |
| Allegion (UK) Limited | Birmingham | 1889 |
| Allegion Safety & Security Solutions Limited | Bury | 2000 |
| Allego Charging Ltd | London | 2017 |
| Allegria of RYE Ltd | Rye | 2026 |
| Allegro Foodservice Ltd | London | 2022 |
| Alleima Limited | London | 2021 |
| Allen & Elliott Limited | Gloucestershire | 1967 |
| Allen & Heath Limited | Cornwall | 2001 |
| Allen & Orr,Limited | Chesterfield | 1909 |
| Allen & Page,Limited | Shipdham Thetford Norfolk | 1936 |
| Allen (Concrete) Limited | Mitcham | 1987 |
| Allen and Company (Industrial Glazing and Painting Specialists) Limited | Bridgend | 1980 |
| Allen Associates (Systems) Ltd | Aberlour | 2016 |
| Allen Automation Limited | West Yorkshire | 2004 |
| Allen Bespoke Metal Ltd | Tring | 2025 |
| Allen Bros Fireplaces Limited | Wigan | 1996 |
| Allen Brothers (Fittings) Limited | Essex | 1958 |
| Allen Christopher Welding Limited | Maesteg | 2008 |
| Allen Diesels Limited | Bedford | 2009 |
| Allen Engineering (Rotherham) Limited | Rotherham | 2003 |
| Allen Fabrications & Sons Ltd | Pontefract | 2004 |
| Allen Fabrications (N.E.) Ltd | Hartlepool | 2017 |
| Allen Fabrications Limited | Evesham | 1963 |
| Allen Farm Services Limited | Telford | 2023 |
| Allen Gearing Solutions Limited | Worcester | 2008 |
| Allen Gwynnes Pumps Limited | London | 2015 |
| Allen Harding Promotions Limited | Hoddesdon | 1996 |
| Allen Hydraulic Engineering Limited | Worcester | 2003 |
| Allen Industrial Controls Ltd | Billingshurst | 2025 |
| Allen Industrial Group Limited | London | 2020 |
| Allen Installations Limited | Brightlingsea | 1996 |
| Allen Jackson Bakery Limited | Chesterfield | 2023 |
| Allen Marmot (European) Limited | Middlesex | 1968 |
| Allen Martin SW Limited | St. Austell | 2019 |
| Allen Organ Services Limited | Aylesbury | 2002 |
| Allen Signs Limited | Lincoln | 1979 |
| Allen Upholstery Ltd | Sheffield | 2017 |
| Allen Works & Co Ltd | London | 2026 |
| Allen's Bespoke Handrail Ltd | London | 2024 |
| Allen's Design & Print Ltd | Stanmore | 2011 |
| Allenby Glass Limited | Lincoln | 1997 |
| Allenby's of Anwick Limited | Grimsby | 2003 |
| Allenchrome Electroplating Limited | York | 1984 |
| Allencompassing Ltd | Lincoln | 2025 |
| Allendale Brew Company Limited | Hexham | 2004 |
| Allendale Components Limited | Redcar | 2003 |
| Allendale Group Ltd | Hoddesdon | 2003 |
| Allenfield Precision Engineering Limited | Didcot | 1965 |
| Allengray Kitchens Limited | Maldon | 2002 |
| Allens Bakery & Confectionery Ltd | Manchester | 2011 |
| Allens Crankshafts Ltd | Nottingham | 2008 |
| Allens Maintenance Services Limited | Sheffield | 2013 |
| Allens Printers Limited | Penarth | 1966 |
| Allens Windows & Doors Ltd | Coventry | 2021 |
| Allensby Group Limited | Hull | 2018 |
| Allensparks Ltd | London | 2012 |
| Allenwest Group Limited | Prestwick | 2010 |
| Allenwest Limited | Prestwick | 2026 |
| Allenwest Wallacetown Limited | Prestwick | 1999 |
| Allequa Ltd | Deeside | 2025 |
| Allequipment Limited | London | 2008 |
| Allergy Free Cakes From Heaven Ltd | London | 2008 |
| Allergy Therapeutics (UK) Limited | West Sussex | 1998 |
| Allergy Therapeutics PLC | West Sussex | 2004 |
| Allerlei Ltd | Bolton | 2022 |
| Allermuir Limited | Accrington | 1986 |
| Allerthorpe Conservatories Ltd. | Pocklington | 2002 |
| Allerton and Company of London Ltd | Oxfordshire | 1988 |
| Allerton Interiors Ltd | Bradford | 2022 |
| Allerton Marine Services Limited | Lowestoft | 2014 |
| Allerton Steel Limited | Northallerton | 2009 |
| Allesley Coachbuilders Limited | Coventry | 2023 |
| Allett Limited | Stafford | 1991 |
| Allevard Springs Limited | Birmingham | 1990 |
| Allevat Limited | Walsall | 2015 |
| Allevent Radio Services Limited | East Sussex | 2004 |
| Allevol Limited | London | 2005 |
| Alley Consultancy Ltd | Watford | 2026 |
| Alley Katz Ltd | Bridgnorth | 2011 |
| Allez Active Ltd | London | 2025 |
| Allez! Bakes Limited | Melton Mowbray | 2023 |
| Allez-Y Limited | Littleborough | 2012 |
| Allfab (Scotland) Limited | Glasgow | 2010 |
| Allfab Electrical & Mechanical Services Ltd | Leeds | 2012 |
| Allfab Ltd | Wolverhampton | 2024 |
| Allfab Services Limited | Hull | 2021 |
| Allfarm Installations Limited | Woodbridge | 1998 |
| Allfine International Co., Ltd. | Beckenham | 2013 |
| Allflex UK Group Limited | Stanley | 2010 |